February 2003. Vanuatu wanted to know of non-chemical methods for nematode control, and this produced many suggestions.
Sunn hemp (Crotataria spp.) is useful in reducing nematodes, especially when incorporated into soil before crops sensitive to nematodes. The University of Hawaii may be able to give more information; also see http://soils.usda.gov/sqi/files/10d3.pdf - it is informative.
From India, a number of suggestions were made:
- Application of native or local isolates of Paecilomyces lilacinus (Pochonia chlamydosporia) and Verticillium chlamydosporium at 100 g of formulation (containing 109 spores/g)/m2 or arbuscular mycorrhizal spores at 108 spores/m2 in the nursery (for transplantable vegetables); this establishes colonization of roots by these beneficial organisms.
- Spot application of the fungal formulations at 30 kg/ha in the field at time of transplant and neem/pongamiya/castor cake at 600 kg/ha.
- Application of vermicompost at 300-500 kg/ha, integrated with fungal formulations.
These treatments need to be repeated over a long time in order to establish the populations in soils on a semi-permanent basis. Application of fungal formulations should follow light irrigation.
1. BioAct WG is a product containing the fungus, Paecilomyces lilacinus, strain 251, dried on glucose. BioAct WG contains 1x1013 active spores per kg of the fungus. The product is formulated as a water-dispersible granulate (application rate 4 kg/ha). BioAct WG is manufactured and developed in Germany by ProPhyta GmbH www.prophyta.com. There are also some documents in French at the following site:
http://www.8ung.at/oesterlin/. It is availabe in New Caledonia. BioAct WG controls a wide range of plant parasitic nematodes including: Radopholus similis - burrowing nematode; Globodera rostochiensis - potato cyst nematode; Meloidogyne spp. - root knot nematodes; Pratylenchus spp. - root lesion nematodes; Heterodera spp. - cyst nematodes; Rotylenchulus reniformis - reniform nematode; Tylenchulus semipenetrans - citrus nematode.
Use Paecilomyces lilacinus with caution; read all the background literature beforehand. VA mycorrhiza as a PRE-planting root dip is extremely effective in controlling nematodes in container plants.
2. Water-extracted neem seed kernels, or just the crushed seed kernels, can be effective controlling soil nematodes. It takes time to become effective. Cardamom growers in India regularly use neem seed waste in their plantations and it is very effective.
Use of neem against nematodes
Neem is used successfully in India for the control of root-knot nematode in vegetable crops. About 5 tonnes per hectare is sufficient if only neem cake is being applied at the planting holes (targeted application). This necessarily means manual application. If tractor drawn manure spreaders are used, the dosage would be 10-15 tonnes per hectare, but then the neem cake will serve the purpose of manure more than as a nematicide.
It was suggested that instead of neem cake (residue from neem oil extraction), the residue from neem-seed-kernel-extract is used as this is also an effective spray against several lepidopteran pests in vegetable crops.
However, it was pointed out that there is no evidence in the scientific literature of neem being a nematicide. In addition, Azadirachtin, the active component of neem, is very quickly decomposed in the soil (half live is less then 2 to 4 days). This makes homogenous distribution in the soil difficult, and (even if it is does kill nematodes) repopulation of the soil will be very quick from deeper layers and from nearby untreated areas. Nematodes are very mobile (more than 1 meter per day).
It is also known, that Azadirachtin is not transported downward from leaves to roots: even after applying very high doses to the leaves, no Azadirachtin can be detected in the roots. Azadirachtin is quickly decomposed inside the plants (half live is about 1 day).
Neem cake will also act as a organic manure. It is well known that large amounts of any organic manure will have some impact on nematode populations.
See: http://www.trifolio-m.de/ for the rage of organisms that can be controlled by neem.
3. Other organic amendments
There were numerous other recommendations: adding large amounts of organic matter to the soil - nematodes often seem to flourish in sandy or dry soil without much organic matter; fallows with black plastic (for one year); using molasses in irrigation systems (e.g., organic banana growers in Queensland, Australia); crop rotation and flood fallows.
Note on quarantine risk
As a caution, it was advised that a weed risk analysis was necessary before considering importation of sunn hemp. The most widely used methodology for weed risk assessment is that developed initially by Paul Phelong in Western Australia and later adapted by Craig Walton and Neil Ellis of AQIS. It is available at: http://www.affa.gov.au/content/output.cfm?ObjectID=D2C48F86-BA1A-11A1-A2200060B0A04014